@article{01533622, title = {Levelling an unknotting tunnel.}, journal = {Geometry \& Topology}, volume = {4}, year = {2000}, pages = {243-275}, doi = {10.2140/gt.2000.4.243}, zbl = {0958.57007}, language = {en}, url = {http://dml.mathdoc.fr/item/01533622} }
Goda, Hiroshi; Scharlemann, Martin; Thompson, Abigail. Levelling an unknotting tunnel.. Geometry & Topology, Tome 4 (2000) pp. 243-275. doi : 10.2140/gt.2000.4.243. http://gdmltest.u-ga.fr/item/01533622/